Its the same cultural problem that some people have with eating dog. Its just a different world. The meat in this case even walks to the place where its needed! If it was a cow or a pig, it would probably seem less objectionable. Horse seems to ring up as "pet" in my mind and so colors the issue for me.

If you think about it, he doesn't need to shoot the horse first. Dropping it to the bottom of the ocean with cinder blocks attached would do the trick while possibly attracting more sharks. It be cheaper and cleaner boat-side as well. He would probably find it morally objectionable to do so though.

If more people had to kill their own meat, there'd be a ton more vegetarians.